Solar panels and wind farms churn out energy around midday and at night when demand lulls.

This forces utilities to discard it in favor of more predictable oil and coal plants and more controllable natural gas “peaker” plants.

2) Technology

Alphabet Inc.’s project named Malta, is working on a molten salt storage system. The system consists of two tanks that are filled with salt, and two are filled with antifreeze or a hydrocarbon liquid. The system takes in energy in the form of electricity and turns it into separate streams of hot and cold air.

The hot air heats up the salt, while the cold air cools the antifreeze. By the flip of a switch the process can be reversed and hot and cold air rush toward each other, creating powerful gusts that spin a turbine and spit out electricity when the grid needs it.

Salt maintains its temperature well, so the system can store energy for many hours, and even days, depending on how insulated the tanks are.